Grinding machine



May 26, 1964 P. D] LELLA 3,134,204

GRINDING MACHINE Filed Sept. 28, 1962 8 Sheets-Sheet l FIG II INVENTOR. Paul DiLe/[a BY Efwnefl ATTORNEY May 26, 1964 P. D! LELLA GRINDING MACHINE 8 Sheets-Sheet 2 Filed Sept. 28, 1962 INVENTOR. Paul DiLe/Ia ATTORNEY May 26, 1964 P. D! LELLA GRINDING MACHINE 8 Sheets-Sheet 4 Filed Sept. 28, 1962 INVENTOR. Paul DiLel/a BY 35. Zmneii W ATTORNEY May 26, 1964 P. DI LELLA GRINDING MACHINE 8 Sheets-Sheet 5 Filed Sept. 28, 1962 FlG 6 INVENTOR. Paul Di Lella ATTORNEY May 26, 1964 Filed Sept. 28, 1962 P. DI LELLA 3,134,204

GRINDING MACHINE 8 Sheets-Sheet 6 INVENTOR. Paul DiLel la ATTORNEY United States Patent 3,134,204 GRINDING MACHEJE Paul Di Lelia, Solvay, N.Y., assignor, by mesne assignments, to E. W. Bliss Company, Canton, Ohio, a corporation of Delaware Filed Sept. 28, 1962, Ser. No. 227,001 11 Claims. (Cl. 51-134.5)

This invention relates to automatic grinding machines, and has as an object a grinding wheel sensing structure which functions automatically, while the grinding wheel is in grinding engagement with a predetermined area of a work piece, to then sense, or determine, the diameter of the grinding wheel, and the arrangement includes means for automatically adjusting the speed of the motor driving the grinding wheel, the horizontal transverse movements of the grinding wheel mount relative to the work piece and the vertical position of the grinding wheel upon initial contact with the work piece, all these adjustments being made in proportion to the diameter of the wheel as sensed by the sensing structure.

The invention is herein disclosed in connection with a grinding machine of the type intended particularly for grinding billets and slabs in steel mills. These grinding machines are relatively large, the electric motor rotating the grinding wheel being of seventy-five or more horse power, with the grinding wheel having an initial diameter of 20 to 24 inches and having a face width of 2 /2 to 3 inches. The work piece is traversed in a linear path below the grinding wheel and upon each reciprocation of the work piece, the grinding Wheel is indexed rearwardly until one side or surface of the billet or slab is completely ground. Compared with usual grinding machines and grinding operations, a relatively large amount of metal is removed from the billet or slab per minute, with the result that there is appreciable wear of the grinding wheel and accordingly, a reduction in its diameter within a relatively short interval of time. A machine of this general type is disclosed in my copending application, Serial Number 97,562, filed March 22, 1961.

The invention consists in the novel features and in the combinations and constructions hereinafter set forth and claimed.

In describing this invention reference is had to the accompanying drawings in which like characters designate corresponding parts in all the views.

In the drawings:

FIGURE 1 is a front elevational view of the center portion of a grinding machine in which my present invention may be embodied.

FIGURE 2 is an end elevational view looking to the right, FIGURE 1, with parts broken away and parts in section.

FIGURE 3 is a front elevational view of the sensing probe actuating mechanism, the cover of the casing being removed.

FIGURE 4 is a view looking to the right, FIGURE 3.

FIGURE 5 is a view looking to the left, FIGURE 3, with parts in section.

FIGURE 6 is an enlarged front elevational view of the probe structure mounted on the grinding wheel guard and showing a contiguous portion of the billet being ground.

FIGURE 7 is a view taken on line 77, FIGURE 6.

FIGURE 8 is a schematic wiring diagram of that portion of the circuitry having to do with the control of the reciprocation of the table 22.

FIGURE 9 is a schematic wiring diagram of the circuity for the grinding wheel motor.

FIGURE 10 is a schematic wiring diagram involving the switches and relays associated with the carriage 33.

FIGURES l1 and 12 are schematic diagrams of the electrical control circuity.

"ice

FIGURE 13 is a view of the structure for controlling retrograde movement of the motor operated positioner device.

Referring briefly to the general arrangement of the grinding machine, it has an elongated base structure 20 provided with rails 21 on which a work supporting table 22 is reciprocated, the table 22 being supported as by a plurality of rollers 23. The work piece, in the form of a billet B, is fixedly secured to the table by side clamping structures 24 and end clamps 25. The table is reciprocated by a reversible motor 26.

Referring to FIGURE 2, there is a second base struc ture 30 having rails 31 extending in a direction transversely to the path in which the table 22 is reciprocated. A carriage 33 is provided with rollers 34 for movement on the rails 31. The carriage is reciprocated on the rails by a cylinder and piston structure 35.

A pair of columns 37 are mounted on the carriage 33 and extend upwardly therefrom. A support 38 is slidably mounted on the columns 37, vertical reciprocation of the support 38 being effected by a reversible motor 40 mounted on a top plate 41 supported by the columns 37. Cables 42 are attached to the support 38 and extend upwardly to drums 43 journalled in suitable supports on the top plate 41. The drums 43 are connected with drums 45 to which cables 46 are attached at their upper ends, and at their lower ends to counterweights 47. By this arrangement, the support 38 is counterbalanced, the weights 47 being positioned within the hollow columns 37.

A grinding wheel mount is carried by the support 38 and includes arms 54 extending forwardly from the support 38 and carrying bearings 56 in which there is journalled a grinding wheel arbor 57. A grinding wheel 69 is secured to the arbor 57. The arbor is rotated by an electric motor '70 fixed to the support 38 and having driving connection with the arbor 57 through a belt 71. The reversible motor 40 is employed to effect rotation of a screw 49 having threaded engagement with a nut attached to the support 38. When the support is moved downwardly a suthcient distance by the motor 40, the grinding wheel 69 engages the billet B.

This invention has to do particularly with a probe apparatus for sensing the diameter of the grinding wheel 69 and varying the speed of the motor 70 in accordance with the wheel diameter to maintain a constant surface speed at the periphery of the grinding wheel which wears down during the grinding operation. As the wheel decreases in diameter, the speed of the motor 70 is increased proportionately to maintain the desired surface speed on the wheel.-

The probe structure, FIGURES 3, 4 and 5, is mounted in a casing including a back plate to which a cover 81 is removably aflixed. The back plate 80 of the casing is fixedly attached to a box-shaped bracket 82 fixedly secured to a side wall, or removable door 84 of the wheel guard 83, the probe casing being disposed vertically. The probe structure, per se, includes a base plate 87 afiixed to the back plate 80, as by screws 88. Aflixed to the base plate 87, as by screws 89, are guide strips 90. The

guide strips 90 extend in spaced parallel relation and are formed on their confronting sides with slots 91.

A plate 92 has its edges slidably mounted in the slots 91, and has affixed to its forward side a gear rack 93, as by screws 94. A block 95 is fixed to the lower end of the plate 92, as by screws 96, the block being positioned intermediate the guide plates 90. A piston rod 97 is fixedly secured to the block 95 and extends into a cylinder 99, the upper end of which is secured to the base plate 87 by nuts 100 engaging the under and upper side of a bracket 101.

A rod 102 is secured at its upper end to the block 95 and extends downwardly through the lower wall 103 of us the cover 81, the rod 102 being slidably mounted in an antifriction bushing 104 mounted in the lower cover wall 103. A bifurcated block 105 is fixed to the lower end of the rod 102, and a roller 107 is journalled in the block 105.

When fluid under pressure is supplied to the upper end of the cylinder 99 through conduit 108 connected to a solenoid valve 109, the piston rod effects downward movement of the block 95 and the rod 102. This downward movement continuing until the roller 107 engages the billet B.

A shaft 110 is journalled in bearing blocks 111 mounted on a bracket 112 fixed to the wall 80 of the casing. A gear 113 is fixed to one end of the shaft 110 and is arranged in mesh with the gear rack 93. A gear 115 is fixed to the opposite end of the shaft 110 and is arranged in mesh with a gear 116 fixed to the shaft of a Selsyn device 117 mounted on a support 118 fixed to the front wall of the cover 81. Accordingly, upon downward movement of the probe, the Selsyn device 117 is rotated by the rack 93, gears 113, 115 and 116. The Selsyn device is part of the means for sensing the extend of the downward movement of the probe 102.

The billet clamping structures 24 include a fixed stationary jaw 119, FEGURE 7, and movable jaws 121 which, as each surface of the billet is ground, are retracted to permit the billet to be turned about its axis to present a new side upwardly for grinding. The end clamps 25 are also moved outwardly from the ends of the billet to release the same for turning. When the fourth side of hte billet has been ground, the jaws 129 are retracted and the clamps 25 released, and a new billet is moved into the clamping structures 24 by a billet loader which functions automatically for the insertion of a fresh billet, pushing the ground billet forwardly from the clamping structures 24. A limit switch 127 is arranged in juxtaposition to one or both of the clamping structures 24, the actuator of this switch being engaged upon the ground billet being moved from the clamping structures. Accordingly, this switch is opened momentarily as the ground billet is moved from the clamping jaws.

The ,billet is clamped by the clamping structures 24 and the ends of the billet are engaged by the end clamps 25 which carry switch actuating shoes 130, 131. The carriage 33 is moved forwardly and the support member 38 is moved downwardly to bring the grinding wheel 69 into engagement with the front corner edge of the billet. The table operating motor 26 is reversed by the shoes 130, 131 alternately actuating switches 133, 134, carried by a bracket 135 fixed to the base structure 20. Upon each reciprocation of the table, the carriage 33 is moved rearwardly whereby the top surface of the billet is ground. Thereafter, the support 38 is raised and the carriage 33 moved forwardly and simultaneously, the billet is rotated about its axis 90 to bring the next adjacent side upwardly by suitable turning mechanism.

These operations are repeated until all four sides of the billet have been ground, whereupon the billet feeding transfer or loader inserts fresh billet in the clamps 24 pushing the ground billet from the clamp.

As previously stated, this invention has to do particularly with periodically determining the diameter of the grinding wheel 69 by moving the probe 102 into engagement with the billet. This engagement is effected while the grinding wheel 69 is in grinding engagement with a predetermined area of the billet. The engagement of the probe with the billet is of short duration. The probing operation occurs while the first side of the billet is being ground and the probe actuating mechanism is then locked out by normally closed limit switch 127 while the second, third and fourth sides of the billet are ground. The switch 127 is mounted adjacent one of the clamps 24 for actuation to open position momentarily by a ground billet being moved from the clamps 24. However, if the billets are of large cross-sectional area and great length, the

1 probe operation may take place on each of the four sides of the billet, in which case the look-out feature is controlled by the switches carried by the end clamps 25.

By using the end clamp switches 145, rather than the switch 127, the probing operation takes place on each of the four sides of the billet, inasmuch as these switches are actuated each time the end clamps are moved from the billet ends as each side is ground.

A switch is fixedly mounted on the base structure 31?. The contacts of the switch 150 are closed when the switch is actuated by a shoe 151 fixedly mounted on the carriage 33. The position of the switch 150 and the shoe 151 is such that the contacts of this switch are closed when the vertical plane passing through the axis of the grinding wheel 69 is spaced a short distance forward from the rear edge of the billet B engaged by the fixed clamping jaws 119. As will be more specifically explained hereinafter, the contacts of the switch 150 have to be closed before the solenoid valve 109 is energized to provide fluid under pressure at the top of the probe actuating cylinder 99. This means that the probe 102, when moved downwardly, engages the billet a predetermined distance from the back edge engaged by the jaw 119. This point of engagement is approximately mid-way between the rear and front edges of the billet of smallest cross sectional dimension ground on the machine. Accordingly, inasmuch as this engagement is determined from the fixed jaws 119, the probe will properly engage the selected area of billets of all larger cross sectional dimensions.

1t will be obvious that inasmuch as the grinding wheel is in grinding engagement with the billet at the time the probe engages the billet, the extent of the downward movement of the probe from rest position indicates the then actual diameter of the grinding wheel. The arrangement of this invention functions not only to adjust the speed of the grinding wheel motor 70, in proportion to the diameter of the wheel, but it also functions to determine the forward and rearward positions of the carriage 33-that is, the positions of the grinding wheel 69, and it further determines the initial down position of the grinding wheel.

The actuation of the probe is also controlled as to take place at approximately the central portion of the billet. This to assure that the probe will engage the billet in an area spaced from the ends of the billet, and will be withdrawn prior to the approach of the end of the billet in the area of the probing structure.

Accordingly, the operating control circuity for the reciprocatory operation of the table is included to a degree in the actuation of the probe mechanism. The table actuating control circuity is shown in the schematic dia gram, FIGURE 8. The motor 26 is operated on direct current provided by a generator 160, the output of which is connected to the motor 26, through wire 161, controller contacts 162, overload device 163. The opposite side of the generator is connected to the motor through wire 164.

The motor 26 is reversed by reversing the current in the field coil of the generator 160. The table travel limit switch 134 is connected to the side 167 of a direct current supply through wire 16%, to wire 169, to the left table travel limit switch 133, wire 170, relay coil 171, wire 172, to the opposite side 173 of the supply. Contacts 175 are connected in shunt with the switch 134 by wires 177, 178. The switch 134 is actuated by the shoe 130, FIGURE 1, when the carriage has reached the end of its travel to the right. Closing of contacts 180, 181, results in connecting field 165 of generator 160 in such manner that the motor 26 is reversed to move the table toward the left. This circuit is established from the side 167, through wire 183, contacts 180, wire 185, field 165, wire 187, contacts 181, wire 188, wire 172, to the opposite side 173. Switch 134 is provided with a contact 189 which is closed when switch 134 is open. Switch 133 is provided with a second contact 191 which is open when switch 133 is closed. Contacts 190 being open, relay coil 191 is de-energized.

When the table reaches its extreme left position, shoe 131 engages switch 133 to move it to open position, deenergizing relay 171 and closing contact 190. It will be appreciated that the shoes 130, 131, are only in actuating engagement with the switches 133, 134, for a short duration of time, inasmuch as the table quickly reverses upon actuation of the respective switches. Accordingly, a circuit is now established from the side 167, through wire 193, closed contacts 189, wire 194, contacts 190, relay coil 191, wire 195 to the opposite side 173. Contacts 197 are connected in shunt with contact 190 to provide a stick circuit to hold the relay in. With the de-energization of relay 171, contacts 130 and 181 are now open. A circuit is now provided to the field coil 165 from the side 167, wire 198, contacts 199, wire 200, field coil 165, wire 201, contacts 203, wire 204 to side 173. It will be observed that this results in connecting the field coil 165 in reverse manner to the supply 167, 173, whereby the output of the generator 160 is reversed to effect reverse rotation of the motor 26 for the movement of the table to the right. It will be observed, referring to the diagram, FIGURE 8, that relay 171 is provided with a fourth contact 205.

Referring now to FIGURE 9, the grinding wheel motor 70 is supplied with power from a generator 206, having a constant voltage output, and being connected to the motor 70 through control contacts 207 of motor starter 208. The circuit including a current sensitive relay 209. When the grinding wheel is in grinding engagement with the billet, the current demand of the motor 70 is such as to eifect closing of relay contacts 210. The speed of the motor 70 is varied by varying the voltage supplied to the motor field 211, this field being connected in series through a variable resistor 212.

A forward travel limit switch 213 is mounted on a plate 481 mounted on the base 30 for movement toward and from switch 150, see FIGURE 2. This switch is actuated by a shoe 214 mounted on the carriage 33. Another switch 215 is mounted on the base structure 30 and is actuated by a shoe 217 mounted on the carriage 33. This switch is referred to as a back travel limit switch.

Referring now to the schematic diagram FIGURE 10, the switch 213 is connected to the side 220 of a supply by wire 221 and through wire 222 to switch 215, wire 223, relay 224, wire 225, to the opposite side 226. A hold circuit is provided for this relay by contacts 227 connected in shunt with the switch 213 by wires 228, 229. Relay 224 is referred to as the back travel relay, and is provided with second contacts 230 and a third pair of contacts 231.

Switch 213 has a second contact 233 which is closed when switch 213 is open. Switch 215 is provided with a second contact 234 which is open when switch 215 is closed. Accordingly, when the switch 213 was closed by shoe 214, contacts 233 were opened. When these contacts are closed, they provide a circuit from the side 220, wire 235, contacts 233, wire 236, contacts 234, when closed, relay coil 237, wire 238, to the side 226. It will be observed that the shoes 214, 217 and 151 also actuate their respective switches for short duration as in the case of the table actuated switches.

When the carriage moves forwardlythat is, to the right FIGURE 2, to its front-most position for grinding operation on a billet of given cross; section size, the switch 213 is closed as previously stated, and relay 224 is pulled in. The contacts 231 of this relay are employed as part of the control for the circuit controlling solenoid valve operation to apply fluid to the forward end of the cylinder 35. That solenoid control circuit also including the table switches, so that after switch 213 is closed, fluid will be admitted to the forward end of the cylinder 35 upon each reciprocation of the table to index the car- 6 riage 33 rearwardly to move the grinding wheel 69 progressively rearwardly across the top face side of the billet.

When the carriage has reached its rearmost position, switch 215 is opened. At this time, of course, switch 213 is not engaged by shoe 214 and therefore it is open. The opening of switch 215 de-energizes relay 224 which, up to the opening of switch 215 has been held energized by the hold circuit including the contacts 227. Opening the switch 215 effects closing of the switch 234. Switch 233 being now closed, power is supplied to the relay 237 which is held by the contacts 240 connected in shunt with the switch 234 by wires 241, 242. This relay being provided with additional contacts 243 connecting a solenoid valve to the rear end of the cylinder 35 to efiect forward movement of the carriage to its selected forward position.

The switches 213, 215 are not mounted directly upon the base 30, but upon mechanism operated by a reversible motor 245 which effects movement of those switches toward and from each other for a purpose to be hereinafter referred to.

There is also a switch 247 mounted intermediate the switches 150, 215, for actuation by a shoe 248 to open position when the grinding wheel 69 is engaging the rear corner edge of the billet. This switch, per se, is not an operating part of the circuitry of this invention other than it is to be kept in mind this switch is closed while the top surface of the billet is being ground.

The general functioning of the various switches and relays has been explained in connection with FIGURES 8, 9, and 10.

Assuming now a billet is being ground on the first side thereof, and the carriage 33 has been indexed rearwardly so that shoe 151 has actuated switch and closed its contacts. Switches 215 and 247, FIGURE 2, have not as yet been actuated to open position by the shoes 217, 248. At this time, the grinding wheel 69 is engaging the billet in proximity to, but spaced from, the rear edge of the billet. Because the grinding wheel 69 is working under load, contacts 210 of the current sensitive relay 209 are closed. Assume also that the table 22 is moving to the left, FIGURE 1, which means that the table left travel limit switch 133 is not engaged as yet by the shoe 131 and accordingly, the associated contact 205, FIG- URE 8, is closed. However, when the table had previously reached the end of its travel to the right, table right travel relay switch 134 was actuated to pull in the table generator left control relay 171, which is held in through its holding contacts and accordingly, its contacts 205 are now closed. Also, the probe assembly, FIGURE 5, is in up position and therefore, block 251 on rack 93 has actuated switch 253 mounted on bracket 101 to close the contacts of the switch.

Referring now to FIGURE 11, a circuit is completed from a side 260 of a supply through wire 261, normally closed contacts 2626 of a relay G, wire 263, closed switch 247, wire 264, contacts 230 of closed relay 224, wire 265, closed contacts 210 of relay 209, wire 266, closed contacts 205 of relay 171, wire 267, closed contacts 250 of table switch 133, wire 268, relay A, wire 269, closed contacts 270C of relay C, wire 271, contacts 272F of relay F, wire 273, switch 253, to the opposite side 275.

Relay A, through its closed contacts 277A energizes the solenoid valve 109 to supply fluid under pressure to the upper end of the probe cylinder 99, to effect downward movement of the probe 102 into engagement with the billet. This circuit extends from the side 260, wire 278, contacts 277A, wire 279, normally closed contacts 280E of relay E, wire 281, solenoid valve 109, wire 282 to the side 275.

Relay A is also provided with a pair of time-delayed contacts 283A, which are timed to close a short interval after the solenoid valve 109 has been energized, and the probe 102 moved downwardly intocontact with the billet. These contacts 283A energize the relay B, the

7 circuit being from the side 260, wire 286, contacts 283A, wire 287, relay B, wire 288, to the opposite side 275.

The relay B is provided with a plurality of contacts, and performs a number of functions. It is provided with a pair of contacts 290B, 291B, which close a circuit from the supply 260, 275, to energize a brake device 293, which is mechanically connected to a Selsyn receiving device 294, upper right, FIGURE 11.

Energization of the brake 293 restrains the Selsyn device 294 from rotation. The Selsyn device 294 is connected to the Selsyn transmitter 117 by wires 295, 296 and 297, and which are connected through normally closed contacts 298D, 299D, 300D, of relay D. It will be understood that the extent of movement of the Selsyn transmitting device 117, upon the descent of the probe to the billet, is transmitted to the Selsyn receiving device 294, the movement of the latter corresponding to the movement of the transmitter 117. As previously stated, relay B is not in the energized state until after the probe has moved downwardly into engagement with the billet. Accordingly, the brake 293, then applied, is effective to hold the Selsyn device 294 in the position into which it has been rotated by the device 117.

Relay B is also provided With contacts 333B for energizing the relay D. This circuit extends from the side 261), through wire 304, normally closed contacts 305C of relay C, wire 307, contacts 303B, wire 308, closed contacts 309E of relay E, wire 310, relay D, wire 311, to the side 275. Relay D is referred to as a transfer relay. When thus energized, its contacts 298D, 299D, 303D, open, disconnecting the Selsyn transmitting device 117 from the Selsyn receiving device 294.

Relay D is also provided with contacts 312D, 313D, which close upon energization of the relay to connect the lines 296, 297, extending from the Selsyn receiver 294, to a full-wave rectifier 315. The output of this rectifier extends through wires 317, 318, to a motor-operated rheostat positioner 320, FIGURE 12, and functions to move the rheostat 212 to a position corresponding to the extent of the downward movement of the probe for varying the voltage in the field 211 of the grinding wheel motor 70 to vary the speed thereof accordingly.

Relay D also has a contact 321D which closes to provide a circuit from the side 260, through wire 322, contact 321D, Wire 323, probe signal timer E, wire 324 to the side 275.

It will be recalled, the table 22 is moving to the left. Prior to the time the right end of the billet approaches the probe, the relay E opens its contacts 280E to open the circuit to the solenoid valve 109 for the admission of fluid to the lower end of the cylinder 99, effecting movement of the probe upwardly to its rest position.

Relay E energizes relay C through contacts 330E. This circuit extending from the side 260, wire 331, closed contacts 333G or relay G, wire 334, closed switch 127, wire 335, contacts 330E, wire 337, relay C, wire 338 to the opposite side 275. The contacts 330E are shunted by contacts 340C to provide a stick circuit for relay C independent of the contacts 330E. Upon energization of relay C, its contacts 270C open. However, relay A is provided with hold contacts 343A providing a shunt circuit about the contacts 27 C, 272F, and switch 253.

Contacts 309E of the probe signal timer E are timedopen contacts, with sufficient time to allow the positioning devices 320 to re-position itself according to the signal from the Selsyn device 294. When these contacts time out and open, they interrupt the circuit to the relay D, this notwithstanding the fact that contacts 305C are open and hold contacts 345D are closed. Accordingly, the contacts 321D open to de-energize the timer E. De-energization of timer E does not de-energize relay C because it is held closed by its holding contacts 340C, and through closed switch 127. Energization of relay C opens contacts 270C. When the left travel limit switch 133, FIG- URE 8, is actuated, relay 171 is de-energized, opening its contacts 235 to break continuity in the circuit to relay A, and relay A is accordingly de-energizcd and the hold contacts 343 open. Accordingly, with contacts 270C held open, there is now no circuit to re-energize relay A to close its contacts 277 to again energize the solenoid valve 109.

In view of this situation, the probe can not move downwardly again until switch 127 is opened to release relay C. Switch 127 is not opened until the ground billet is removed from the clamping structures 24. Accordingly, the probe is not moved downwardly on the second, third and fourth sides of the billet.

If one of the end clamp switches is substituted for the switch 127, then relay C would be de-energized after each side of the billet was ground because the end clamps 25, carrying the switches 145, have to be moved outwardly from engagement with the ends of the billet after each side is ground to permit the billet to be turned and reclamped.

In connection with the grinding of round work pieces, they are mounted on the table 22 for rotation. The carriage 33 is fixedly positioned so that the carriage travel switches 213 and 215 are not actuated. The round work pieces are rotatively indexed upon reciprocation of the work table. The grinding wheel 69 accordingly remains in constant grinding engagement with the round work piece. This invention includes an arrangement for periodically effecting descent of the probe into the engagement with the round work piece.

Referring to the left portion of FIGURE 11, switch contacts 350, 351 and 352 are mechanically actuated by a timer motor 353, this connection being indicated by the dashed line 354. Switches 3511, 351 and 352 are normally open and are periodically closed by the motor 353. Relay G is energized by the closing of manual switch contacts 355. Relay G is energized when round work pieces are ground. When relay C is dc-energized, its contacts 262G in the energized circuit of relay A are closed, and also its contacts 333G in the energized circuit of relay C are closed. When relay G is energized and contacts 262G and 333G open, contacts 357G and 359G close to provide an energizing circuit for relay A when contacts 350 are closed. Contacts 3586 close, shunting the carriage probe switch for the continuous energization of relay F. This is due to the fact that in grinding a round work piece, the carriage 33 is not moved along the rails 31 and accordingly, the carriage probe limit switch 150 does not get to be actuated.

An additional contact 360G is closed in the circuit to the timer motor 353. The circuit for the motor 353 is from the side 2611, closed relay contacts 367C, wire 369, closed contacts 360G, closed contacts 362 of the grinder load relay 209, FIGURE 9, wire 363, motor 353, wire 365, to the side 275.

After an interval of time, for example four minutes, the motor 353 will open contacts 350, 351, 352. However, during that interval those contacts remain closed. Accordingly, a circuit is completed from the side 260, through the closed contacts 350 and 357G to wire 263. The rest of the circuity for relay A is completed, as previously described, in connection with the grinding of work pieces of rectangular cross-section, and in like manner, the sequential operation of relays B, D, E and C take place in the manner previously described to effect descent of the probe 102 downwardly for a momentary engagement with the work piece, and for the adjustment of the rheostat 212 to provide for the correct speed of the grinding wheel driving motor 70.

After the expiration of the time interval, the motor 353 will open the switches 350, 351, 352, the opening of the switch 351 disconnecting the wire 335 from the side 260 to cause the relay C to become de-energized, closing its contacts 367C to immediately energize the motor 353 to recycle the probe operation. In other words, the switch 351 now controls the energizing circuit to relay C, due to the fact that the switch 127 is not actuated in the grinding of the round work piece. When relay C is de-energized, its contacts 270C close and accordingly, the energizing circuit for relay A is again established when the contacts 350 close. In this portion of the operation, the circuit is not interrupted to the motor 353 by the opening of contacts 352 because these contacts are shunted by the contacts 367C of relay C, and close upon de-energization of relay C to provide a shunt circuit from side 269, wire 368, contacts 367C, wire 369, to wire 361, so there is no interruption in the operation of the motor 353. The opening of the contacts 350, 351, 352 is only momentary.

Accordingly, as long as the switch 355 is closed to hold relay G energized and contact 262 of load relay 209 is closed, the probe 102 will be periodically moved downwardly to the work piece for sensing the diameter of the grinding wheel 69, and adjusting the speed of its driving motor 70 accordingly.

In brief review, in regard to grinding rectangular billets, and making reference to FIGURE 2, the jaws 119 of the billet clamping structures are fixed jaws so that the rear side of the billet is always in a fixed position. Accordingly, the carriage 33 has to be moved forwardlythat is, to the right, FIGURE 2, a sufficient distance for the grinding wheel 69 to engage and grind the front corner edge of the billet. Basically, the forwardmost position of the carriage is determined by the cross-sectional dimension of the billet. In other words, the carriage has to move forwardly a greater distance if a billet six inches square is being ground, than it would if the billet were two inches square.

Another factor in determining the forwardmost and rearwardmost position of the carriage 33 is the diameter of the grinding wheel 69. When the wheel is of full size, or maximum diameter, the carriage 33 has to be positioned forwardly and rearwardly a greater distance than it does when the wheel has worn down to lesser diameter. By the same token, it will be apparent that the initial down position of the wheel mount varies according to the diameter of the grinding wheel 69.

This invention also includes an ararngement for automatically varying the forwardmost and rearwardmost position of the carriage and grinding mount, and also its initial vertical position, in proportion to the grinding wheel diameter. It 'will be recalled that the motor operated rheostat positioning device 320 is energized by the output of the rectifier 315 through wires 317, 318. The device 320 being mechanically connected to the rheostat 212 and functioned to position it in accordance with the voltage on the line 317, 318, which, in turn, is in proportion to the grinding wheel diameter.

The positioning device 320 is also mechanically connected to a movable contact 400, see FIGURE 12, and when energized, functions to move the contact 400 to the right successively into engagement with fixed contacts 401-416. These contacts 401, 416, are connected the wire 420 to the side 421 of a supply. Assume now the positioning device 329 has been energized, effecting movement of the contact 490 into engagement with the contact 481. A circuit is completed from side 421, wire 420, contacts 401, 400, buss strip 423, wire 424, relay M, wire 426, to the opposite side 427 of the supply. This circuit also extends through branch wire 428, relay N, wire 430, the relays M and N being connected in parallel. Relay M is the vertical wheel wear timer relay. Relay N is the horizontal wheel wear timer relay.

Relay M is provided with time open contacts 431M, normally closed, and which time open. Relay M is also provided with contacts 433M that close instantaneously when the relay is energized. In like manner, relay N is provided with time open contacts 434N and also with instantaneous contacts 435N. These contacts serve, when the relays M and N are energized, to energize a wheel wear hold relay P, the circuit being from wires 421, 429, 437, 438, through closed contacts 431M, wire 440, closed 14) contacts 433M, wires 441, 442, relay P, wire 443, to the side 427. The contacts 434N are connected by wire 445 to the contacts 435N, this latter pair of contacts being connected in shunt with contacts 431M and 433M. A pilot light 447 is connected in shunt with the relay P.

The relay P has a pair of contacts 450P. These contacts serve to provide a stick circuit for the relays M and N, the circuit being from wire 42%), wire 437, contacts 4501, wire 452, to wire 424. The relay P is also provided with a pair of normally closed contacts 453P connected in the line 318 to the positioning device 320.

With this arrangement, the relay P is energized upon the contact 400 engaging the first fixed contact 401, and the opening of the contacts 453P disconnect the positioner 320 :from the rectifiier 315 and accordingly, the movable contact 400 is stopped from further movement. Relay M has a second time open contact 455M, lower portion in FIGURE 12, and a regular contact 456M. With relay M energized, a circuit is provided from source side 421, wire 457, contacts 455M, wire 458, contacts 456M, wire 459, contacts 460, to motor contactor 461, wire 462, to the side 427. The contactor 461, when energized, energizes the motor 463, FIGURE 2, in such direction as to move the plate 465 downwardly. An ilp-limi-t switch 467, and a down-limit switch 468 are mounted on the plate 465. These switches are engaged by an arm 469 carried on the support 38. When the limit switch 468 is engaged by the arm 469 upon downward movement of the support 38, current is interrupted to the motor 40. Accordingly, the down position of the grinding wheel 69 is determined by actuation of the switch 468 by the arm 469. With this arrangement, as the wheel 69 wears down and decreases in diameter, the switch plate 465 is moved downwardly to effect a new down position for the grinding wheel 69.

The relay N is likewise provided with time open contacts 4711N and with contacts 471N, which are closed when the relay N is energized. This establishes a circuit from the side 421, through wire 473, wire 474, contacts 470N, wire 475, contacts 471N, wire 477, contacts 478, contactor 479, Wire 4811, to the opposite side 427. The contactor 479, when thus energized, energizes the motor 245, FIGURE 2, to move plate 481 to the left, so that the forward position limit switch 483 will be actuated by the carriage shoe 214 to reduce the forward movement of the carriage, this adjustment in like manner being commensurate to the wear of the grinding wheel 69. The motor also simultaneously moves the switches 215, 247, to the right to relocate the rearmost position of the carriage 33.

Normally, closed contacts 460 are associated with a motor contactor 485, and contacts 478 are associated with a motor contactor 486. As will be explained hereinafter,

I, at times the contactor 485 is energized to cause motor 463 to move the switch plate 465 upwardly. Also, contactor 486 is energized to cause the motor 245 to move the switch plate 481 forwardly, these contactors 485, 486, being energized at the initial start of the machine to reset the wheel mount in its full-up and forwardmost and rearwardmost positions. The circuit to contactor 485 also includes normally closed contacts 487, associated with contactor 461, and the circuit to the contactor 486 includes normally closed contacts 488, associated with contactor 479. The purpose of the contacts 460', 487, is simply to provide a lock-out circuit, so when either contactor 461, or 485, is energized, the other can not be energized, and the same applies as to the contactors 479, 486.

The length of time the contactors 461, 479, are energized depends upon the setting of the time open contacts 455M, 479N of the relay timers M and N respectively, this time being sufficient to effect movement of the switch plates 465, 481, a predetermined distance.

It is to be remembered, the relays M and N are locked in through the contacts 4501, and the positioning device 1 i 320 is de-energized by the opening of contacts 4531. This situation prevails until both of the time open contacts 431M and 434N time out. The timing of these contacts is somewhat greater than the timing of the contacts 455M, 470N. As the contacts 431M and 434N time out, relay P is dropped, opening its contacts 456i, dropping out the relays M and N, and reclosing contacts 453P in the circuit to the positioner 320. If the signal impressed on the rectifier 315 by the Selsyn device 2% is of sufiicient voltage to effect further movement of the positioning device 320, it will advance the movable contact 400 to the contact 402, whereupon the circuity described is re-established, and the switch plates 465, 481, are adjusted another increment. The purpose of the lochin circuit for the relays M, N, through contacts 4-56? is to take care of the possibility that the positioner device 320 may advance the contact 4% intermediate the pair of contacts 401, 416. With this arrangement, it will be apparent that the down position of the grinding wheel 6 and its forwardmost and rearwardmost posit-ions are adjusted in proportion to the wear on the grinding wheel 6?.

This invention further includes an arrangement whereby, before the operator can start the grinding machine, it is compulsory that he first elfect movement of the carriage to probe position, and then cause descent of the probe into engagement with the billet. Upon descent of the probe the diameter of the grinding wheel is sensed and the various adjustments effect it automatically as previously explained.

Relay S is also provided with contacts 517$, establishing a circuit from side 421, wire 473, contacts 517$, wire 518, closed contacts 488 of contactor 479, contactor 486, wires 520, 480, to the side 427. As previously stated, the contactor 486, when energized, furnishes current to the motor 245 to operate it in such direction as to move the switch plate 481, FIGURE 2, to the full forward position. Accordingly, when the machine is next put into operation, the grinding wheel 69 will be in the full up and full forward positions corresponding to full, or maximum diameter of the grinding wheel 69, and for the grinding of a billet of maximum cross sectional dimension as, for example, -a six-inch billet. Also, the positioning device 329 is returned to star-ting position. If a billet of smaller cross-sectional dimension is placed in the machine, the operator energizes the motor 490 by a manual switch to move the shoe 214 forwardly in position corresponding to the smaller size billet. Also, by the same manual switch he operates motor 463 to adjust the plate 465 to position the up and down limit switches 467, 468.

However, before the operator can start the grinding wheel motor 70, he must effect movement of the carriage 33 to locate the probe 102 in probing position, and must effect descent of the probe into engagement with the billet.

The reason for this is as follows:

Energized relay S also has contacts 5258, which are now engaged, establishing a circuit to relay T from side 421, wire 526, contacts 525$, wire 527, relay T, wire 528, to the side 427. Relay T has normally closed contacts 529T, FIGURE 9, in the circuit to the motor starter 2038, these contacts being now open so motor '70 can not be started until relay T is de-energized, which can not take place until the operator has caused the probe 162 to move down into engagement with the billet. Contacts of energized relay T set up the circuit to permit the operator to perform this initial probe operation.

There is a pilot light 539, FIGURE 11, connected in shunt with the relay F. The light 539 is energized by the closing of the carriage probe limit switch 150 by shoe 151 when the carriage 33 is positioned to cause the descending probe to engage the selected probe area of the billet, as previously described. As just previously mentioned, when the grinding wheel motor is shut off, the motors 245, 463, are operated to automatically position switches 12 213, 468 as to permit the carriage to move for full wheel condition. This, by the operation of relay S.

In order to eifect operation of the probe, the operator now eifects application of fluid pressure to the cylinder 35, FIGURE 2, to effect movement of the carriage 33 until the switch 15h is closed, energizing the light 530 and the relay F. The purpose of the pilot light 530 is to inform the operator that the machine is positioned horizontally in probe position. This provides a circuit from the side $21, through Wire 5335, closed contacts 531R Wire 5354, closed contacts 535T, wires 53d, 537, to push button contacts 538, which are manually closed by the operator, wire 539, relay U, wire 54), to the side 427. Relay U is a relay timer. One of its functions, when energized, is to supply the motor 40, FIGURES l and 2, with limited power to effect operation of the motor in such direction as to move the support 3% downwardly. This downward movement continues until the grinding wheel 69 engages the billet, whereupon the operator releases the push button 53%. Push button contacts 538 are mechanically linked with contacts 543, 544, FIGURE 12, and 545, FIGURE 11, the latter closing when contacts 538 open. Referring to FIGURE ll, a circuit is now established from the side 26%, through wire 5%, timed contacts 547U of relay U, closed push button contacts 545, to relay A which, thus energized, initiates the probing operation, as previously described, with the exception that the transfer relay D is now held in through closed timed contacts 549U.

When the push button arrangement was pressed downwardly by the operator, a circuit was also established to relay V through the push button contacts 544, this circuit extending from wire 536 contacts 55tiU, wire 551, contacts 54-4, wire 552, relay V, wire 553, to the side 427. The relay V is provided with hold contacts 555V shunting the push button contact 544. and contacts 559U. Relay U is also provided with contacts 557U. These contacts are time closed contactsthat is, they close a predetermined time after relay U is tie-energized. The arrangement is such that when contacts 557U time out and close, the probe 102 has been moved downwardly into engagement with the billet. The positioner 329 has advanced contact 4% and adjustable resistor 212 to proper position comparable to wheel diameter as determined by probe 102. Relay T is a latched-in relay having a trip coil 560. A circuit is now completed to the trip coil from wire 421, wire 533, closed contacts 531F, wire 534, closed contacts 535T, closed contacts 563V, wire 564, closed contacts 557U, wire 565, closed push button contacts 543, wire 567, trip coil 5MB, wire 568, to the side 427, unlatching the relay T and opening its contacts 535T, de-energizes relays U and V. Back contacts 529T of relay T, FIGURE 9, now close to re-establish the circuit to the motor starter 208 to permit the same to be started by closing the manual switch 500, and the machine to be put in automatic operation.

When the machine was shut down by the de-energization of the motor starter 203, the contacts 501 opened, de-energizing relay R, and energizing relay S. The motor operated positioning device 324 is provided with a ratchet wheel 58%, FIGURE 13. The teeth of the ratchet wheel 58% are engaged by a spring-pressed pawl 581, the arrangement being such as to permit operation of the device 320 in the forward direction by the output of the rectifier 3315, the pawl serving to prevent retrograde movement of the device by torsion spring 582. A solenoid 583 is operable when energized to raise the pawl 581 out of engagement with the teeth of the ratchet wheel 580 to permit the positioning device to return to initial position. The solenoid 583 is energized by contacts 5848 of relay S. As previously explained relay S is energized when motor starter 268 is de-energizedthat is, when the machine is shut down. Accordingly, when that happens, the positioner device 320 and the contact 400 are returned to start position. The positioning device 320 is provided with an actuator 585, which, when the device is in initial position, engages a stop pin 586, FIGURE 12. When the device 320 has been actuated to move the contact 400 to full forward position in engagement with the contact 416, the actuator 585 actuates a switch 587 causing its normally closed contacts 588 to open. These contacts, FIGURE 9, are included in a stick circuit for the motor starter 208, the stick circuit being connected in shunt with the manual start switch 500.

With this arrangement, if the operator starts up the machine with the grinding wheel 69 already worn down to the minimum diameter, operation of the sensing probe will cause the contact 400 to be moved to full forward position in engagement with the contact 416 and contacts 588 of switch 587 to be opened, so that the machine can not be operated with the worn out wheel. This stick circuit extends from line 590, through wire 591, stick contacts 592 of the starter 208, wire 593, contacts 588, wire 594, contacts 529T, to the starter 208, the opposite side of which is connected to the return wire 595.

What I claim is:

l. A grinding machine comprising a work support table having clamping means for clamping a work piece in fixed position thereon, means operable to effect reciprocation of said table over a fixed linear path, a support mounted for vertical movement, a grinding wheel mount carried by said support including an arbor and a grinding wheel mounted on said arbor, a motor operatively connected to said arbor to effect rotation thereof, means operable to move said support downwardly to move said grinding wheel into grinding engagement with the work piece on said table, a probe carried by said wheel mount and movable from an up rest position downwardly into engagement with the work piece, means operable for effecting such downward movement of said probe While said grinding wheel is in grinding engagement with the work piece, sensing means for sensing the extent of the downward movement of said probe from said rest position, and means operable by said sensing means to adjust the speed of said motor in proportion to the extent of movement of said probe.

2. A grinding machine comprising a work support table having clamping means for clamping a work piece in fixed position thereon, means operable to effect reciprocation of said table over a fixed linear path, a support mounted for vertical movement, a grinding wheel mount carried by said support including an arbor and a grinding wheel mounted on said arbor, a motor operatively connected to said arbor to effect rotation thereof, means operable to move said support downwardly to move said grinding wheel into grinding engagement with the work piece on said table, a probe carried by said wheel mount and movable from an up rest position downwardly intoengagement with the work piece, means operable for effecting such downward movement of said probe while said grinding wheel is in grinding engagement with a selected area of the work piece, sensing means for sensing the extent of the downward movement of said probe from said rest position, and means operable by said sensing means to adjust the speed of said motor in proportion to the extent of movement of said probe.

3. A grinding machine comprising a work support table having clamping means for clamping a work piece in fixed position thereon, means operable to effect reciprocation of said table over a fixed linear path, a support mounted for vertical movement, a grinding wheel mount carried by said support including an arbor and a grinding wheel mounted on said arbor, a motor operatively connected to said arbor to effect rotation thereof, means operable to move said support downwardly to move said grinding wheel into grinding engagement with the work piece on said table, a probe carried by said Wheel mount and movable from an up rest position downwardly into engagement with the work piece, means operable for effecting such downward movement of said probe, while said grinding wheel is in grinding engagement with a selected area of the work piece intermediate the ends thereof and retracting said probe prior to the movement of an end of the work piece in proximity to the probe, sensing means for sensing the extent of the downward movement of said probe from said rest position, and means operable by said sensing mean to adjust the speed of said motor in proportion to the extent of movement of said probe.

4. A grinding machine as defined in claim 3, including means operable to maintain said probe in engagement with the work piece for a predetermined time.

5. A grinding machine comprising a work supporting table having clamping means for clamping a work piece in fixed position thereon, means operable to effect reciprocation of said table over a fixed linear path, a carriage, a support mounted on said carriage for vertical movement toward and from the plane of said table, a grinding wheel mount carried by said support above said table and including an arbor, and a grinding wheel mounted on said arbor, a motor operatively connected to said arbor for effecting rotation thereof, means for moving said support downwardly to move said grinding Wheel into grinding engagement with the work piece, means operable upon reciprocation of said table to move said carriage successively from a forward position to a rear position to effect movement of the grinding wheel transversely of the work piece, a probe carried by said wheel mount and movable from an up rest position downwardly into engagement with the work piece, means for effecting such downward movement of said probe while said grinding wheel is in grinding engagement with the work piece, sensing means for sensing the extent of the downward movement of said probe from said rest position, and means operable by said sensing means to limit the forward and rearward movement of said carriage in proportion to the extent of movement of said probe.

6. A grinding machine comprising a work support table having clamping means for clamping a work piece in fixed position thereon, a support mounted for vertical movement, a grinding wheel mount carried by said support including an arbor and a grinding wheel mounted on said arbor, a motor operatively connected to said arbor to effect rotation thereof, means operable to move said support downwardly to move said grinding wheel into grinding engagement with the work piece on said table, and means operable to effect relative reciprocation between said table, and said support, a probe carried by said wheel mount and movable from an up rest position downwardly into engagement with the workpiece, means operable for effecting such downward movement of said probe while said grinding wheel is in grinding engagement with the work piece, sensing means for sensing the extent of the downward movement of said probe from said rest position, and means operable by said sensing means to adjust the speed of said motor in proportion to the extent of movement of said probe.

7. A grinding machine comprising a work support table having clamping means for clamping a work piece in fixed position thereon, means operable to effect reciprocation of said table over a fixed linear path, a support mounted for vertical movement, a grinding wheel mount carried by said support including an arbor and a grinding wheel mounted on said arbor, an electric motor operatively connected to said arbor to effect rotation thereof, means operable to move said support downwardly to move said grinding wheel into grinding engagement with a work piece clamped on said table, a probe housing carried by said wheel mount, a probe mounted in said housing for movement from a rest position in a direction radially of the grinding wheel, means operable to effect movement of said probe in said radial direction into engagement with a selected area of the work piece while said grinding wheel is in grinding engagement with the work piece, a transmitting Selsyn device operatively connected to said probe for rotation thereby upon movement of said probe from rest position into engagement with the work piece, a receiving Selsyn device connected to said transmitting device for movement in unison therewith and having an output circuit, the voltage of which varies in proportion to the extent of movement of said Selsyn devices, means connected to said output circuit and operable to adjust the speed of said motor in proportion to the voltage on said output circuit.

8. A grinding machine comprising a work support table having clamping means for clamping a work piece in fixed position thereon, means operable to effect reciprocation of said table over a fixed linear path, a support mounted for vertical movement, a grinding wheel mount carried by said support above said table and including an arbor and a grinding wheel mounted on said arbor, a motor operatively connected to said arbor to effect rotation thereof, means operable to move said support downwardly to move said grinding wheel into grinding engagement with the work piece on said table, a probe carried by said wheel mount and movable from an up rest position downwardly into engagement with the work piece on said table, probe actuating means operable for effecting downward movement of said probe in engagement with a selected area of the work piece for a predetermined time and thence returning said probe to up rest position, sensing means for sensing the extent of the downward movement of said probe from said rest position, and means operable by said sensing means to adjust the speed of said motor in proportion to the extent of the downward movement of said probe.

9. A grinding machine as defined in claim 8, including means for rendering said probe actuating means inoperable for repetitive downward movement of said probe until said work piece is removed from the work support table.

10. A grinding machine comprising a work support table having clamping means for clamping a work piece in fixed position thereon, means operable to effect reciprocation of said table over a fixed linear path, a support mounted for vertical movement, a grinding wheel mount carried by said support and including an arbor journalled for rotation and a grinding Wheel mounted on said arbor,

an electric motor operatively connected to said arbor to effect rotation thereof, means for moving said support downwardly to move said grinding wheel into grinding engagement with the work piece on said table, a probe carried by said wheel mount and movable from an up rest position downwardly into engagement with the work piece, probe actuating means operable for effecting such downward movement of said probe while said grinding wheel is in grinding engagement with the work piece, sensing means for sensing the extent of the downward movement of said probe from said rest position, and means operable by said sensing means, when said probe has descended a predetermined distance from said up rest position, to de-energize said motor.

11. A grinding machine comprising a work support table reciprocable over a fixed linear path and having clamping means for clamping a work piece in fixed position, a support mounted for vertical movement in a direction toward and from the plane of said table, a grinding wheel mount carried by said support and including an arbor journalled for rotation and a grinding wheel fixedly secured thereto, a motor operatively connected to said arbor to effect rotation thereof, means operable to move said support downwardly to move said grinding wheel in engagement with the work piece on said table, a motor energizing means, a probe carried by said wheel mount for movement from an up rest position downwardly into engagement with the work piece on said table, means operable for effecting such downward movement of said probe when said grinding wheel is engaging the work piece, and for returning said probe to said up rest position, and means operable, upon the return of said probe, to render said motor energizing means effective to energize said motor.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noe 3 134M204 May 26 1964 Paul Di Lella It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 22 for extend" read extent, line 31,, for "hte" read the column 8 line 3 for "343" read 343A line 5 for "277" read 277A Signed and sealed this 29th day of September 1964 (SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W; SWIDER Altesting Officer 

1. A GRINDING MACHINE COMPRISING A WORK SUPPORT TABLE HAVING CLAMPING MEANS FOR CLAMPING A WORK PIECE IN FIXED POSITION THEREON, MEANS OPERABLE TO EFFECT RECIPROCATION OF SAID TABLE OVER A FIXED LINEAR PATH, A SUPPORT MOUNTED FOR VERTICAL MOVEMENT, A GRINDING WHEEL MOUNT CARRIED BY SAID SUPPORT INCLUDING AN ARBOR AND A GRINDING WHEEL MOUNTED ON SAID ARBOR, A MOTOR OPERATIVELY CONNECTED TO SAID ARBOR TO EFFECT ROTATION THEREOF, MEANS OPERABLE TO MOVE SAID SUPPORT DOWNWARDLY TO MOVE SAID GRINDING WHEEL INTO GRINDING ENGAGEMENT WITH THE WORK PICE ON SAID TABLE, A PROBE CARRIED BY SAID WHEEL MOUNT AND MOVABLE FROM AN UP REST POSITION DOWNWARDLY INTO ENGAGEMENT WITH THE WORK PIECE, MEANS OPERABLE FOR EFFECTING SUCH DOWNWARD MOVEMENT OF SAID PROBE WHILE SAID GRINDING WHEEL IS IN GRINDING ENGAGEMENT WITH THE WORK PIECE, SENSING MEANS FOR SENSING THE EXTENT OF THE DOWNWARD MOVEMENT OF SAID PROBE FROM SAID REST POSITION, AND MEANS OPERABLE BY SAID SENSING MEANS TO ADJUST THE SPEED OF SAID MOTOR IN PROPORTION TO THE EXTENT OF MOVEMENT OF SAID PROBE. 